On Sun, Mar 29, 2020 at 8:34 AM Hauke Mehrtens <ha...@hauke-m.de> wrote:
>
> On 3/27/20 5:28 AM, Yousong Zhou wrote:
> > The patch is backported from mips-next. In addition to minor reduction
> > of code size and runtime memory use, the more apparent difference is
> > that the delay slot emulation page will not be present for those targets
> > with fpu emulation disabled (CONFIG_MIPS_FP_SUPPORT=n)
> >
> > Memory maps of busybox before and after this change
> >
> > root@OpenWrt:/# cat /proc/self/maps
> > 00400000-00449000 r-xp 00000000 00:02 23 /bin/busybox
> > 00458000-00459000 r-xp 00048000 00:02 23 /bin/busybox
> > 00459000-0045a000 rwxp 00049000 00:02 23 /bin/busybox
> > 77dc0000-77de2000 r-xp 00000000 00:02 273 /lib/libgcc_s.so.1
> > 77de2000-77de3000 r-xp 00012000 00:02 273 /lib/libgcc_s.so.1
> > 77de3000-77de4000 rwxp 00013000 00:02 273 /lib/libgcc_s.so.1
> > 77de4000-77e7b000 r-xp 00000000 00:02 271 /lib/libc.so
> > 77e8a000-77e8c000 rwxp 00096000 00:02 271 /lib/libc.so
> > 77e8c000-77e8e000 rwxp 00000000 00:00 0
> > 7fd86000-7fda7000 rw-p 00000000 00:00 0 [stack]
> > 7fefd000-7fefe000 r-xp 00000000 00:00 0
> > 7ffe6000-7ffe7000 r--p 00000000 00:00 0 [vvar]
> > 7ffe7000-7ffe8000 r-xp 00000000 00:00 0 [vdso]
> >
> > root@OpenWrt:/# cat /proc/self/maps
> > 00400000-00449000 r-xp 00000000 00:02 23 /bin/busybox
> > 00458000-00459000 r-xp 00048000 00:02 23 /bin/busybox
> > 00459000-0045a000 rwxp 00049000 00:02 23 /bin/busybox
> > 77d55000-77d77000 r-xp 00000000 00:02 274 /lib/libgcc_s.so.1
> > 77d77000-77d78000 r-xp 00012000 00:02 274 /lib/libgcc_s.so.1
> > 77d78000-77d79000 rwxp 00013000 00:02 274 /lib/libgcc_s.so.1
> > 77d79000-77e10000 r-xp 00000000 00:02 272 /lib/libc.so
> > 77e1f000-77e21000 rwxp 00096000 00:02 272 /lib/libc.so
> > 77e21000-77e23000 rwxp 00000000 00:00 0
> > 7fe23000-7fe44000 rw-p 00000000 00:00 0 [stack]
> > 7ff63000-7ff64000 r--p 00000000 00:00 0 [vvar]
> > 7ff64000-7ff65000 r-xp 00000000 00:00 0 [vdso]
> >
> > Signed-off-by: Yousong Zhou <yszhou4t...@gmail.com>
>
> Acked-by: Hauke Mehrtens <ha...@hauke-m.de>
Acked-by: Rosen Penev <ros...@gmail.com>
I have the previous version of this patch (taken from ldir's tree) in
my tree. Works great. Have not seen any problems.
>
> > ---
> > ...e-dsemul-code-when-CONFIG_MIPS_FP_SU.patch | 140 ++++++++++++++++++
> > 1 file changed, 140 insertions(+)
> > create mode 100644
> > target/linux/generic/backport-5.4/300-MIPS-Exclude-more-dsemul-code-when-CONFIG_MIPS_FP_SU.patch
> >
> > diff --git
> > a/target/linux/generic/backport-5.4/300-MIPS-Exclude-more-dsemul-code-when-CONFIG_MIPS_FP_SU.patch
> >
> > b/target/linux/generic/backport-5.4/300-MIPS-Exclude-more-dsemul-code-when-CONFIG_MIPS_FP_SU.patch
> > new file mode 100644
> > index 0000000000..1be051e1df
> > --- /dev/null
> > +++
> > b/target/linux/generic/backport-5.4/300-MIPS-Exclude-more-dsemul-code-when-CONFIG_MIPS_FP_SU.patch
> > @@ -0,0 +1,140 @@
> > +From d96c3157f9ca177727fbad960fcf6f52f145f471 Mon Sep 17 00:00:00 2001
> > +From: Yousong Zhou <yszhou4t...@gmail.com>
> > +Date: Thu, 9 Jan 2020 11:33:19 +0800
> > +Subject: [PATCH] MIPS: Exclude more dsemul code when
> > CONFIG_MIPS_FP_SUPPORT=n
> > +
> > +This furthers what commit 42b10815d559 ("MIPS: Don't compile math-emu
> > +when CONFIG_MIPS_FP_SUPPORT=n") has done
> > +
> > +Signed-off-by: Yousong Zhou <yszhou4t...@gmail.com>
> > +---
> > + arch/mips/include/asm/processor.h | 12 ++++++------
> > + arch/mips/kernel/process.c | 10 ++++++++--
> > + arch/mips/kernel/vdso.c | 26 +++++++++++++++-----------
> > + 3 files changed, 29 insertions(+), 19 deletions(-)
> > +
> > +diff --git a/arch/mips/include/asm/processor.h
> > b/arch/mips/include/asm/processor.h
> > +index 7619ad319400..813ba94d87bb 100644
> > +--- a/arch/mips/include/asm/processor.h
> > ++++ b/arch/mips/include/asm/processor.h
> > +@@ -253,13 +253,13 @@ struct thread_struct {
> > + #ifdef CONFIG_MIPS_FP_SUPPORT
> > + /* Saved fpu/fpu emulator stuff. */
> > + struct mips_fpu_struct fpu FPU_ALIGN;
> > +-#endif
> > + /* Assigned branch delay slot 'emulation' frame */
> > + atomic_t bd_emu_frame;
> > + /* PC of the branch from a branch delay slot 'emulation' */
> > + unsigned long bd_emu_branch_pc;
> > + /* PC to continue from following a branch delay slot 'emulation' */
> > + unsigned long bd_emu_cont_pc;
> > ++#endif
> > + #ifdef CONFIG_MIPS_MT_FPAFF
> > + /* Emulated instruction count */
> > + unsigned long emulated_fp;
> > +@@ -302,7 +302,11 @@ struct thread_struct {
> > + .fpr = {{{0,},},}, \
> > + .fcr31 = 0, \
> > + .msacsr = 0, \
> > +- },
> > ++ }, \
> > ++ /* Delay slot emulation */ \
> > ++ .bd_emu_frame = ATOMIC_INIT(BD_EMUFRAME_NONE), \
> > ++ .bd_emu_branch_pc = 0, \
> > ++ .bd_emu_cont_pc = 0,
> > + #else
> > + # define FPU_INIT
> > + #endif
> > +@@ -334,10 +338,6 @@ struct thread_struct {
> > + * FPU affinity state (null if not FPAFF) \
> > + */ \
> > + FPAFF_INIT \
> > +- /* Delay slot emulation */ \
> > +- .bd_emu_frame = ATOMIC_INIT(BD_EMUFRAME_NONE), \
> > +- .bd_emu_branch_pc = 0, \
> > +- .bd_emu_cont_pc = 0, \
> > + /* \
> > + * Saved DSP stuff \
> > + */ \
> > +diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
> > +index 339870ed92f7..b2a797557825 100644
> > +--- a/arch/mips/kernel/process.c
> > ++++ b/arch/mips/kernel/process.c
> > +@@ -75,7 +75,9 @@ void start_thread(struct pt_regs * regs, unsigned long
> > pc, unsigned long sp)
> > + lose_fpu(0);
> > + clear_thread_flag(TIF_MSA_CTX_LIVE);
> > + clear_used_math();
> > ++#ifdef CONFIG_MIPS_FP_SUPPORT
> > + atomic_set(¤t->thread.bd_emu_frame, BD_EMUFRAME_NONE);
> > ++#endif
> > + init_dsp();
> > + regs->cp0_epc = pc;
> > + regs->regs[29] = sp;
> > +@@ -176,7 +178,9 @@ int copy_thread_tls(unsigned long clone_flags,
> > unsigned long usp,
> > + clear_tsk_thread_flag(p, TIF_FPUBOUND);
> > + #endif /* CONFIG_MIPS_MT_FPAFF */
> > +
> > ++#ifdef CONFIG_MIPS_FP_SUPPORT
> > + atomic_set(&p->thread.bd_emu_frame, BD_EMUFRAME_NONE);
> > ++#endif
> > +
> > + if (clone_flags & CLONE_SETTLS)
> > + ti->tp_value = tls;
> > +@@ -650,8 +654,10 @@ unsigned long mips_stack_top(void)
> > + {
> > + unsigned long top = TASK_SIZE & PAGE_MASK;
> > +
> > +- /* One page for branch delay slot "emulation" */
> > +- top -= PAGE_SIZE;
> > ++ if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
> > ++ /* One page for branch delay slot "emulation" */
> > ++ top -= PAGE_SIZE;
> > ++ }
> > +
> > + /* Space for the VDSO, data page & GIC user page */
> > + top -= PAGE_ALIGN(current->thread.abi->vdso->size);
> > +diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c
> > +index bc35f8499111..3adb7354bc01 100644
> > +--- a/arch/mips/kernel/vdso.c
> > ++++ b/arch/mips/kernel/vdso.c
> > +@@ -71,10 +71,12 @@ subsys_initcall(init_vdso);
> > +
> > + static unsigned long vdso_base(void)
> > + {
> > +- unsigned long base;
> > ++ unsigned long base = STACK_TOP;
> > +
> > +- /* Skip the delay slot emulation page */
> > +- base = STACK_TOP + PAGE_SIZE;
> > ++ if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
> > ++ /* Skip the delay slot emulation page */
> > ++ base += PAGE_SIZE;
> > ++ }
> > +
> > + if (current->flags & PF_RANDOMIZE) {
> > + base += get_random_int() & (VDSO_RANDOMIZE_SIZE - 1);
> > +@@ -95,14 +97,16 @@ int arch_setup_additional_pages(struct linux_binprm
> > *bprm, int uses_interp)
> > + if (down_write_killable(&mm->mmap_sem))
> > + return -EINTR;
> > +
> > +- /* Map delay slot emulation page */
> > +- base = mmap_region(NULL, STACK_TOP, PAGE_SIZE,
> > +- VM_READ | VM_EXEC |
> > +- VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
> > +- 0, NULL);
> > +- if (IS_ERR_VALUE(base)) {
> > +- ret = base;
> > +- goto out;
> > ++ if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
> > ++ /* Map delay slot emulation page */
> > ++ base = mmap_region(NULL, STACK_TOP, PAGE_SIZE,
> > ++ VM_READ | VM_EXEC |
> > ++ VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
> > ++ 0, NULL);
> > ++ if (IS_ERR_VALUE(base)) {
> > ++ ret = base;
> > ++ goto out;
> > ++ }
> > + }
> > +
> > + /*
> >
>
>
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